This invention relates to an apparatus for controlling the operation of an electric vehicle.
In prior art electric vehicle stop means, such as described in Japanese patent No. 2-65604, it is well known that brake torque is generated in the drive motor to hold the vehicle in a stop, and to help stop the vehicle on a slope. In this arrangement, such torque is always generated to prevent the vehicle from sliding down the hill.
Japanese patent No. 53-20268 discloses an ultrasonic sensor arrangement for detecting the approach of a vehicle, such as a fork lift, to within a specified distance from a load. In this device, a pulse generator is used to sense the distance between the vehicle and load, and to stop the vehicle at a specified distance from the load.
In the prior art control devices, when stopping an electric vehicle on a slope, the operator must apply sufficient braking force mechanically by means of a brake. If insufficient mechanical braking force is applied, an undesirable vibration results from switching of the motor between backward and forward torques. Although such vibration diminishes and stops with the passage of time, the actual stop position depends on the gradient of the slope, which is a problem.
Although the above mentioned prior art devices can stop a traveling vehicle at a specified position, the possibility of motion of the vehicle after the stop is not considered, and if the vehicle stops on a slope, there still exists a problem of undesired movement of the vehicle after stopping. Moreover, the above two prior art devices also suffer from the disadvantage that an electric vehicle cannot be moved from an initial stop position to a desired second position and held there by a simple operation.